1. Field of the Invention:
This invention lies in the field of drilling masts or derricks for deep boreholes, such as those drilled for the production of hydrocarbon gases and liquids. More particularly, it concerns a type of construction in which the derrick can be transported simply and reliably and yet can be, with minimum effort, raised with cables into an extended vertical position and locked with removable drive pins.
2. Description of the Prior Art:
There have been many designs of large drilling derricks which can support tremendous weights of pipe in the hole. However, all of the designs for large masts have been of the so-called jackknife type where pieces of the derrick are laid out on the ground and assembled piece-by-piece into the final mast or derrick structure. By hinging two of the four legs to corresponding points on a base structure on the ground and by using special cable arrangements, the derrick is lifted from a horizontal into a vertical position. The erection of these large masts must be without the use of separate lifting cranes, which would not be available in the areas where the derrick would be used.
Other types of derricks or masts have been built by assembling the derrick structure piece-by-piece in a vertical position by means of a crane to lift the various pieces of the assembly to the topmost position of the derrick. Again, such large cranes that would be needed would not be available in most of the areas where such a large derrick would be required. Therefore, this unique method of assembling everything on the ground in a collapsed form and then raising and extending the telescoping sections offers an entirely new freedom in the design and the strength of the structure.